1. Field of the Invention
The present invention is generally related to a method for measuring zeta potential, and more particularly to a method for measuring the zeta potential of the cylinder's outer surface and measurement system thereof.
2. Description of the Prior Art
Membrane technology was focused on flat membrane during early development while the development of tubular membrane was started around in 1960s from hollow-fiber membrane used in gas separation made by DuPont. Because hollow-fiber membrane has advantages of high specific surface area per unit volume and self-supporting property, it is extensively applied in gas separation, reverse osmosis, hemodialysis, ultrafiltration, microfiltration, and so forth.
Membrane electric charge generally plays an important role in determining its separation performance. Currently, the measurement of zeta potential of membrane focuses on flat membranes. In practice, tubular membrane has been extensively applied in the industry but there is no method provided to measure the zeta potential of the outer surface of tubular membrane. Thus, generally the industry or researchers accept the information supplied by the manufacturer to qualitatively determine the charge property of the membrane. However, membrane electric charges are affected by not only material of the membrane but also the property of solution, such as pH value and ionic intensity. Since there is no effective method provided to quantitatively characterize the charge of the outer surface of cylindrical type objects, therefore it is required to develop a method and measurement system for measuring zeta potential of the cylinder's outer surface, especially the zeta potential of the outer surface of cylindrical membranes. According to the zeta potential, filtration conditions designed to reduce the membrane fouling can be provided and thus the filtration capacity and the selectivity in separation can be enhanced.